This invention relates to manufacturing pipe insulation and more particularly to an apparatus and method for making pipe insulation.
In order to manufacture a cylindrical insulation product suitable for insulating pipes, an insulating material such as mineral fibre is first formed into a cylindrical shape. After the insulation product has been formed, it is typically hardened in this shape by curing. After curing, it may be necessary or desirable to sand the exterior of the hardened cylindrical product in order to provide a regular, smooth exterior.
U.S. Pat. No. 3,344,009 (Levecque) discloses an apparatus for forming hollow cylinders of resin-impregnated mineral mats suitable for use as insulation for systems of pipes or conduits. The apparatus includes a mandrel about which the mat is wrapped. The winding of the mat on the mandrel is executed pneumatically, in that the hollow mandrel has perforations on its surface, and the interior of the mandrel is placed under reduced pressure. After the mat has been formed on the mandrel, it is ejected therefrom and travels through a heating compartment that heats the mat to a sufficient temperature and for a sufficient period of time to cure the mat.
Prior apparatus such as that disclosed by Levecque may suffer from a number of disadvantages. Typically, the mineral fibre used for insulation is somewhat resilient. If, as is typically the case, the mineral fibre is no longer subjected to compression after forming, then there may be some expansion of the compressed mineral fibre before curing. The expanded mineral fibre will then be cured, resulting in an insulation product that may be of lower density than desired. Further, it is very desirable that the insulation product have a hard and smooth inside core as well as uniform wall thickness and outside diameter, as this greatly facilitates fitting the insulation on pipes. The concentricity and outside diameter are as important as the inside diameter of the pipe since segments are cut and rotated 180 degrees to form segmented elbows; if the insulation product is not concentric or the outside diameter changes, then the inside diameter of each segment will not line up. Typically, however, the insulation is removed from the forming mandrel before being fully cured. Accordingly, some of the expansion, which may well be uneven, may occur on the inner surface of the insulation product as well as the outer surface of the insulation product, resulting in a cured inside core that is less hard and smooth than the core was at the end of the forming stage of manufacture. The insulation product may also differ in thickness at different points along its length as a result of differential expansion.
Prior apparatus for winding insulating ply around a cylindrical core have been devised. U.S. Pat. No. 5,143,314 (Soikkeli), issued on Sep. 1992, discloses such a prior apparatus in which an insulating material is wound around the core and a movable endless belt is bent around both the core and the insulating material in order to compress and form the insulating material around the core.
Prior art apparatus such as the Soikkeli apparatus may suffer from a number of disadvantages. For example, the movable endless belt used by Soikkeli to hold and compress the insulating material next to the core may not provide equal pressure on the insulating material all the way around the core. Indeed, at some points, the mineral fibre may not be contacted by the endless belt at all, resulting in uneven thickness and density of the insulation material after forming. Further, in the Soikkeli apparatus the forming radius provided by the endless belt cannot be separately controlled; instead this forming radius is determined by the tension in the endless belt and the resistance of the insulation product to compression. This, in turn, may make it more difficult to produce high tolerance insulation product, especially when forming low density outer layers of insulation. High tolerance insulation product is desirable for, among other applications, fabricating segmented sections of insulation to fit curved pipe.
Thus, a method and apparatus for manufacturing pipe insulation in which the insulation is kept on the mandrel or core throughout both the curing stage and the forming stage, and in which the desired shape and density of the insulation product can be retained throughout the forming stage and the curing stage, is desirable. Preferably, the apparatus for manufacturing pipe insulation would include a roll forming apparatus that provides substantially uniform compression to all exposed portions of the insulating material around its circumference. It is also desirable that the rolling apparatus be easily and precisely adjustable to accommodate changes in the diameter of the insulating material and core. In order to integrate the forming of the insulation product with subsequent stages of manufacture, such as curing and sanding, it is desirable that the core with the formed insulating material wrapped thereround be easily transportable to the subsequent curing stage.
An object of an aspect of the present invention is to provide an improved insulation manufacturing apparatus.
In accordance with this aspect of the present invention there is provided a roll forming apparatus for rolling a selected material around a cylindrical core. The apparatus comprises a core support, a roll support means, and a material supply means. The core support is for supporting the cylindrical core. The core support has an associated core rotation means for rotating the core about a core rotation axis at a controllable rotation rate. The roll support means supports a plurality of forming rolls positioned to surround the core about the core rotation axis. The roll support means has a roll control means operable to both radially position the plurality of forming rolls relative to the core rotation axis and to constrain the plurality of forming rolls to be equally spaced from the core rotation axis, in order to provide integrated adjustment of the plurality of forming rolls to control a radial dimension of a substantially symmetrical forming space defined by the plurality of forming rolls. The material supply means is for supplying the selected material to the core at a material supply rate, and has an associated material supply control means for controlling the material supply rate.
In accordance with another aspect of the present invention there is provided an apparatus for receiving a selected curable material and for retaining the selected curable material during a forming stage and a curing stage. The selected curable material is formed into a desired configuration during the forming stage, and is heated during the curing stage to harden the selected material in the desired configuration. The apparatus includes a core mounted for rotation about an axis of rotation, a curing means for heating the selected curable material to at least a curing temperature to harden the selected curable material in the selected configuration, and a vacuum means in fluid communication with the fluid communication means. The core has an associated core rotation means for rotating the core about an axis of rotation, an outer permeable surface for receiving and retaining the selected curable material, and a fluid communication means for receiving air flow from the outer permeable surface. The vacuum means is operable to draw a forming core air flow through the fluid communication means, the outer permeable surface of the core and the selected curable material retained on the core during forming of the selected curable material retained on the core. The forming core air flow has a temperature below the curing temperature. The vacuum means is also operable to draw a curing core air flow through the outer permeable surface and the fluid communication means of the core and the selected curable material retained on the core during curing of the selected curable material retained on the core.
An object of another aspect of the present invention is to provide an improved insulation manufacturing method.
In accordance with this aspect of the present invention there is provided a method of forming and curing a selected curable material in a desired configuration. The method comprises the steps of (a) supplying the selected curable material to the core, (b) forming the selected curable material retained on the core, and (c) curing the selected curable material retained on the core. During steps (a), (b) and (c), the method also comprises drawing a core air flow through a permeable surface of a core and through the selected curable material on the core to retain the selected curable material on the core and to compress the selected permeable material to the core. The core air flow has an air temperature below a curing temperature of the selected curable material during steps (a) and (b).